Method of producing materials in finely-divided form



J. E. HARRIS Dec. l0, 1929.

METHOD OF PRODUCING MATERIALS IN FINELY DIVIDED FORM Filed Jan. 51, 1929 IAI /NVENTUR ..1 E. HARP/S mechanically into' dust, and in Patented Dan 1o, 1929 UNITED STATES PATENT oFFicE JAMES E. HARRIS, 0F NEWARK, NEW JERSEY, ASSIGNOR TO BELL TELEPHONE LAB- ORATORIES, INCORPORATED, OF NEW YORKyN. Y., A CORPORATION ,OF NEW YORK METHOD OF PRODUCING MATERIALS IN FINELY-DIVIDED FORM Application med yJanuary si, 1929. serial No. 336,418.

This invention relates to methodsof producing ma eljals in finely divided form and particularl to methods of producing finely divided magnetic materials.

The invention has special reference to methods of manufacturing finely divided magnetic material for use in magnetic cores of the so-called dust type, particularly dust cores for loading coils and the like formed from a mixture of finely divided magnetic material and insulating material, such as described in U. S. patent to G. W. Elmen, No. 1,297,126, issued March 11, 1919. In magneticl cores of the type referred to above, it is desirable that the magnetic material be in sufficiently fine sub-division so that eddy currents are reduced to a minimum. Alloys of magnetic materials, such as'nickel, iron and cobalt, because of their good electrical and magnetic characteristics, have been found to be particularly suitable as the magnetic material in such cores. In order to produce finely divided magnetic dust from such alloys in some cases it has been found to be desirable to incorporate in the magnetic alloy a small percentage of an additional material, for example, iron oxide, to embrittle the alloy so that it may be easily broken up subject the material while it is hot to mechanical working, such as rolling, to reduce the size of its crystals so that sufficiently fine dust may be obtained by the subseqpent 'crushing processes. Such a process is described in the U. S. patent to Beath and Heinicke, No. 1,669,649, issued May 15, 1928.

The object of this invention is to facilitate the reduction of metallic materials, such as magnetic alloys, to very finely divided form.

It has been found that the process of the prior art described above is not particularly suitable for reducing certain magnetic materials, for example, alloys including certain proportions of nickel, iron and cobalt, to dust, masmuch as the cr ystals of these materials cannot be 'sufficient y reduced in size by the hot rolling process so as to enable dust of the desired degree of fineness to be produced. In accordance with this invention, the above described process has been improved in the "cated in the drawing.

addition to case of said certain materials by substituting for the step of hot rolling in the process, the step of casting the molten magnetic material, or the molten magnetic material and the incorporated embrittling material, if an embrittling material is used, in water to solidify it, and to produce a crystalline structure therein which is sufiiciently fine to enable the reduction of the material into very fine particles by the subsequent mechanical treatment.

The exact nature of the invention will be understood from the following detailed description thereof When read in connection with the accompanying drawing, the single figure of which shows in schematic form a process for producing finely divided material in accordance with the principles of the invention.

The invention will be described as applied to the production of finely divided magnetic material, but is not limited to magnetic material, but is of advantage in connection with the reduction to very finely divided form of.

metallic materials in general. The various steps in the process of the invention are indi- A preferable detailed method of practicing the invention will now be described. i

,The magnetic -material in solid form -is laced in a suitable container and heated until 1t becomes molten. A small quantity of embrittling material, such as iron oxide or iron sulphide, is then added tothe molten material and mixed thoroughly therewith. This step in the process may, of course, be omitted if thc magnetic material is inherently of the required brittleness so mechanical processes. The molten material is then poured intoY water in a suitable container, the water bein preferably continuously stirred during t e pouringw The material will solidify in the water in the form of brittle aggregates of fine grained crystalline structure. These aggregates are then readily broken up into fine dust by mechanical processes, such as crushing and rolling. In these aggregates the fracture will takeplace principally along the crystal boundaries, and thus,

that it may be readily y reduced to finely divided form by the usual the line rained structure of the material will and to produce a finegrained crystalline enable '51e Imaterial to be reduced to very structure therein, and breaking up the result-` linely divided form' approximating the size ing product into finely divided form., f of a single crysta The method 'of reducing metallic ma- 5 The process ofthe invention which has terial to very finely divided form which conbeen described may be used'for vreduc sists in ineltin the magnetic material, addmetallic materials in Eeneral to iinelv divid mg an embritt ing agent to the molten maform, but it is especially applicableto magterial, casting the molten mixture in water netic alloys such as are used in magnetic dust to solidify it, and to reduce a line-grained m cores for loading.coils,`transformers and the crystalline vstructure lierein, and thereafter 75 like. Its use has been found to be especially mechanically breakin up the resulting proddesirable in connection with the reduction uct into particles .of tie desired lineness. to finely-divided form of a magnetic alloyA 3. The method of reducing a magnetic macontainingabout 45' percent nickel, 30 r terial to a finely divided form suitable for cent cobalt and therest'iroman alloy which ...use 1n lowloss magnetic dust cores for inso has been found especially suitable as a magduction coils, which method consists'in melte netic material for loading signaling lines being t e magnetic material, incorporating an cause of its desirable magnetic and electrical embrittling material in the molten material,

characteristics. -This particular alloy does casting-the molten mixture in waterto solidinot lend itself readily to the processes ofthe it, and to produce a iineaiiied` crystal- 85 prior art forA making magnetic dust because line structure therein, an .mechamcally` i the hotl rolling step 'in such processes in this breaking up the'resulting product into small case will not suliiciently reduce the size of particles. the crystals to enable subdivision of the ma- 4. The method of reducing an alloy includvterial into verviinelv divided form. ing nickel, iron and cobalt to finely divided 90 The fine-grained, brittle magnetic material form suit-able for use in low loss magnetic made by the rocess of the invention is thendust cores for induction coils, which method mechanically roken up into ne dust, as by consists in melting -the alloy, vincorporating crushingand rolling in a ball The maan embrittling material in the molten alloy,

3o terial thus treated will yield a large percentpouring the molten material into watento es age of particles small enough to pas through solidify it, and to produce afine-grained a 120 mesh sieve, particles 'of such ineness cr stalline structure therein,- and mechanibeing particularly suitable for either continca y breaking up the resulting product into uous'or lump' loadin of telephone circuits. small articles. f I

This 'very finely divi ed material is particu- 5. e methodof making a 'magnetic body 10o -larly well adapted to be formed into havin high permeability and low hysteresis or cores for loading coils by a method similar and edy current losses, 'which method conto that described in U. S. tent 'to Andrews sists .invmeltin a magnetic material includet al., No. 1,669,643, issued ay 15, 1928. The ing nickel ang iron, incorporating an em- '40 method described in that patent consists in brittling material in the 'molten material, 105 first 'annealin the magnetic particles, coatpouring the, molten mixture into water to ing the annea ed particles with a suitable insolidif'mit,- andto produce a fine-grained sulating material, and-thenformingthe coatcrystal e structure therein, mechanically ed particles into rings or cores by the a plibreaking iip the resulting roduct into line cation of high Eressure thereto,the resulting dust, insulating the partie es of dust, and 11i rings or cores ein'g given a subsequent anforming the insulated dust intov a homonealing heat treatment to produce the desired genequs solid body.

stable magnetic properties therein'. A plu- In witness whereof,.I hereunto subscribe rality of rings thus formed are then stacked my name this 30th day of January, 1929.

5e coaxia` ly to form a core on which the vusual l JAMES E. HARRIS. iis

toi-oda winding is mounted, the number-of `such rings used depending upon the existing electrical characteristics of the telephone circuit with which the loading coils are to be associated.

, The invention is not limitedv in its a plica.-

, tion to particular materials mention above Awhich are given by way of example onl nor -to the'details in the process describe but onl -by the scope' of the appended claims. f 125 at is claimed is: v '1.' The method Aof reducing metallic niaterial Ato very finely divided form which con- 'sists in melting the metallic material, casting 05 the moltenmaterial in waterto solidify it, lll 

